The present invention relates to firing mechanisms for revolvers. More particularly, it relates to indexing mechanisms for automatically and sequentially rotating the cartridge chambers of a revolver's cylinder into proper firing alignment with the revolver's barrel.
Traditionally, indexing of a revolver has been achieved by a pawl or hand that is attached to the trigger and which engages a tiny ratchet that is centrally located on the rear face of the chambered cylinder. When the trigger is pulled, the hand moves vertically, engages a tooth of the ratchet and causes the cylinder to rotate.
A long-standing and well-recognized problem occurs with the "hand-and-ratchet" system. In order to obtain consistently accurate alignment of all of the chambers in the cylinder of a revolver, extremely close manufacturing tolerances are required in machining the ratchet teeth and in forming the engagement surfaces on the hand that engages the teeth. Since even close tolerances cannot invariably assure the accuracy required of quality revolvers, skilled hand-filing of these parts is usually necessary in the manufacture of a first-rate revolver. This obviously involves considerable expense.
Any imperfection in the fittings of the hand and ratchet cause a magnified error in the amount that the cylinder rotates. As taught in basic geometry courses, a slight variation near the center of a wheel in the angle or distance between two adjacent spokes results in a much greater difference in the length of the arc between the spokes at the rim of the wheel. Similarly, any imperfection between two teeth of the ratchet will cause the cylinder to rotate either too much or too little for exact alignment of the next firing chamber.
If the cartridge chamber is not aligned at the time the contained cartridge is fired, the bullet or slug in traveling from the chamber into the barrel will partially strike and shave itself on the barrel end, thereby causing dangerous splattering of lead, possible jamming of the mechanism, and distortion of the head of the slug, which, in turn, causes inaccuracy in the flight of the projectile after it leaves the barrel.
Even though skilled workers may do their best, there is always the risk of some misalignment. To overcome misalignment, several auxiliary systems have been introduced by which a stop means is used in conjunction with the hand and ratchet to precisely align the cylinder. The stop usually comprises a spring-loaded member which engages a recess in the cylinder during rotation of it to slightly move the cylinder into full alignment if necessary. In addition to correcting slight under-rotation, the stop also locks the cylinder in place and prevents over-rotation.
While these stop mechanisms are useful, they are often fragile and subject to wear. Further, they often require extremely precise timing of the trigger movement to disengage the stop from the cylinder prior to engagement of the hand with the ratchet to start rotation of the cylinder.
Accordingly, it is the primary object of the present invention to provide a new indexing system for rotating and timing a revolver cylinder that eliminates the undesirable characteristics of the "hand-and-ratchet" system presently used in revolvers.
It is another primary object to provide an indexing device which produces a more accurate index than the standard "hand-and-ratchet" system and which eliminates the need for precise fitting of parts at assembly.
It is another object to provide an improved indexing mechanism that is relatively compact and which does not require an auxiliary stop means to insure precise alignment of all the cartridge chambers with the revolver's barrel.
It is yet another object to provide a durable modular indexing unit which can be easily replaced should the need arise.
It is still a further object to provide an improved indexing mechanism for a revolver which is of relatively simple design, which may be assembled in the weapon quite easily, which can be manufactured without the skilled techniques of a gunsmith, and which can be maintained quite easily.